Recently, there has been interest in personalized printing on (or inside) bindery line "books", as the folded sections (signatures) are gathered on the bindery equipment. Ink jet printing is a currently preferred way to accomplish such on-line personalizing; and U.S. Pat. No. 4,395,031 describes a very useful system for enabling ink jet printing on the books which are assembled, but still on the bindery system conveyor chain. This system uses a device referred to as a "plow", which causes the book to open in a manner allowing print head access to an interior page(s).
The plow device described in the '031 patent is a generally rectangular, planar member located along the bindery line, generally within a plane that extends radially from a line defined by the path of the conveyor chain. The upstream end of the planar member is tapered in toward the conveyor chain to form a plow tip portion which impacts the interior lead edges of signatures that are above a plow wire, which extends upstream from the plow tip. The plow surface deflects the engaged signatures outwardly and upwardly as they move past it, in the downstream direction. Ink jet print heads are located beneath the plate-like plow member to print on the exposed signature page.
While the plow device described in the '031 patent functions reasonably well, there is a real problem as to signatures flapping open too far, or falling off the bindery chain. This problem worsens as bindery speeds increase. The system in the '031 patent provides rollers to bias the spines of signatures against the chain, thereby preventing signatures from lifting off the chain; however, it would be desirable to avoid the need for such bias rollers. Also, the rollers cannot prevent the non-constrained portions of the signature from flapping up and down into contact with print heads, which carry ink debris that would mar the signature. Further, signatures flapping into contact with other parts of the apparatus can cause major paper jams.